csharp/qrcode/decoder/FormatInformation.cs

   1 /*\r
   2 * Copyright 2007 ZXing authors\r
   3 *\r
   4 * Licensed under the Apache License, Version 2.0 (the "License");\r
   5 * you may not use this file except in compliance with the License.\r
   6 * You may obtain a copy of the License at\r
   7 *\r
   8 *      http://www.apache.org/licenses/LICENSE-2.0\r
   9 *\r
  10 * Unless required by applicable law or agreed to in writing, software\r
  11 * distributed under the License is distributed on an "AS IS" BASIS,\r
  12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
  13 * See the License for the specific language governing permissions and\r
  14 * limitations under the License.\r
  15 */\r
  16 using System;\r
  17 namespace com.google.zxing.qrcode.decoder\r
  18 {\r
  19         \r
  20         /// <summary> <p>Encapsulates a QR Code's format information, including the data mask used and\r
  21         /// error correction level.</p>\r
  22         /// \r
  23         /// </summary>\r
  24         /// <author>  Sean Owen\r
  25         /// </author>\r
  26         /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source \r
  27         /// </author>\r
  28         /// <seealso cref="DataMask">\r
  29         /// </seealso>\r
  30         /// <seealso cref="ErrorCorrectionLevel">\r
  31         /// </seealso>\r
  32         sealed class FormatInformation\r
  33         {\r
  34                 internal ErrorCorrectionLevel ErrorCorrectionLevel\r
  35                 {\r
  36                         get\r
  37                         {\r
  38                                 return errorCorrectionLevel;\r
  39                         }\r
  40                         \r
  41                 }\r
  42                 internal sbyte DataMask\r
  43                 {\r
  44                         get\r
  45                         {\r
  46                                 return dataMask;\r
  47                         }\r
  48                         \r
  49                 }\r
  50                 \r
  51                 private const int FORMAT_INFO_MASK_QR = 0x5412;\r
  52                 \r
  53                 /// <summary> See ISO 18004:2006, Annex C, Table C.1</summary>\r
  54                 //UPGRADE_NOTE: Final was removed from the declaration of 'FORMAT_INFO_DECODE_LOOKUP'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  55                 private static readonly int[][] FORMAT_INFO_DECODE_LOOKUP = new int[][]{new int[]{0x5412, 0x00}, new int[]{0x5125, 0x01}, new int[]{0x5E7C, 0x02}, new int[]{0x5B4B, 0x03}, new int[]{0x45F9, 0x04}, new int[]{0x40CE, 0x05}, new int[]{0x4F97, 0x06}, new int[]{0x4AA0, 0x07}, new int[]{0x77C4, 0x08}, new int[]{0x72F3, 0x09}, new int[]{0x7DAA, 0x0A}, new int[]{0x789D, 0x0B}, new int[]{0x662F, 0x0C}, new int[]{0x6318, 0x0D}, new int[]{0x6C41, 0x0E}, new int[]{0x6976, 0x0F}, new int[]{0x1689, 0x10}, new int[]{0x13BE, 0x11}, new int[]{0x1CE7, 0x12}, new int[]{0x19D0, 0x13}, new int[]{0x0762, 0x14}, new int[]{0x0255, 0x15}, new int[]{0x0D0C, 0x16}, new int[]{0x083B, 0x17}, new int[]{0x355F, 0x18}, new int[]{0x3068, 0x19}, new int[]{0x3F31, 0x1A}, new int[]{0x3A06, 0x1B}, new int[]{0x24B4, 0x1C}, new int[]{0x2183, 0x1D}, new int[]{0x2EDA, 0x1E}, new int[]{0x2BED, 0x1F}};\r
  56                 \r
  57                 /// <summary> Offset i holds the number of 1 bits in the binary representation of i</summary>\r
  58                 //UPGRADE_NOTE: Final was removed from the declaration of 'BITS_SET_IN_HALF_BYTE'. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  59                 private static readonly int[] BITS_SET_IN_HALF_BYTE = new int[]{0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4};\r
  60                 \r
  61                 //UPGRADE_NOTE: Final was removed from the declaration of 'errorCorrectionLevel '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  62                 private ErrorCorrectionLevel errorCorrectionLevel;\r
  63                 //UPGRADE_NOTE: Final was removed from the declaration of 'dataMask '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
  64                 private sbyte dataMask;\r
  65                 \r
  66                 private FormatInformation(int formatInfo)\r
  67                 {\r
  68                         // Bits 3,4\r
  69                         errorCorrectionLevel = ErrorCorrectionLevel.forBits((formatInfo >> 3) & 0x03);\r
  70                         // Bottom 3 bits\r
  71                         dataMask = (sbyte) (formatInfo & 0x07);\r
  72                 }\r
  73                 \r
  74                 internal static int numBitsDiffering(int a, int b)\r
  75                 {\r
  76                         a ^= b; // a now has a 1 bit exactly where its bit differs with b's\r
  77                         // Count bits set quickly with a series of lookups:\r
  78                         return BITS_SET_IN_HALF_BYTE[a & 0x0F] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 4) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 8) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 12) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 16) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 20) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 24) & 0x0F)] + BITS_SET_IN_HALF_BYTE[(SupportClass.URShift(a, 28) & 0x0F)];\r
  79                 }\r
  80                 \r
  81                 /// <param name="maskedFormatInfo">format info indicator, with mask still applied\r
  82                 /// </param>\r
  83                 /// <returns> information about the format it specifies, or <code>null</code>\r
  84                 /// if doesn't seem to match any known pattern\r
  85                 /// </returns>\r
  86                 internal static FormatInformation decodeFormatInformation(int maskedFormatInfo)\r
  87                 {\r
  88                         FormatInformation formatInfo = doDecodeFormatInformation(maskedFormatInfo);\r
  89                         if (formatInfo != null)\r
  90                         {\r
  91                                 return formatInfo;\r
  92                         }\r
  93                         // Should return null, but, some QR codes apparently\r
  94                         // do not mask this info. Try again by actually masking the pattern\r
  95                         // first\r
  96                         return doDecodeFormatInformation(maskedFormatInfo ^ FORMAT_INFO_MASK_QR);\r
  97                 }\r
  98                 \r
  99                 private static FormatInformation doDecodeFormatInformation(int maskedFormatInfo)\r
 100                 {\r
 101                         // Find the int in FORMAT_INFO_DECODE_LOOKUP with fewest bits differing\r
 102                         int bestDifference = System.Int32.MaxValue;\r
 103                         int bestFormatInfo = 0;\r
 104                         for (int i = 0; i < FORMAT_INFO_DECODE_LOOKUP.Length; i++)\r
 105                         {\r
 106                                 int[] decodeInfo = FORMAT_INFO_DECODE_LOOKUP[i];\r
 107                                 int targetInfo = decodeInfo[0];\r
 108                                 if (targetInfo == maskedFormatInfo)\r
 109                                 {\r
 110                                         // Found an exact match\r
 111                                         return new FormatInformation(decodeInfo[1]);\r
 112                                 }\r
 113                                 int bitsDifference = numBitsDiffering(maskedFormatInfo, targetInfo);\r
 114                                 if (bitsDifference < bestDifference)\r
 115                                 {\r
 116                                         bestFormatInfo = decodeInfo[1];\r
 117                                         bestDifference = bitsDifference;\r
 118                                 }\r
 119                         }\r
 120                         // Hamming distance of the 32 masked codes is 7, by construction, so <= 3 bits\r
 121                         // differing means we found a match\r
 122                         if (bestDifference <= 3)\r
 123                         {\r
 124                                 return new FormatInformation(bestFormatInfo);\r
 125                         }\r
 126                         return null;\r
 127                 }\r
 128                 \r
 129                 public override int GetHashCode()\r
 130                 {\r
 131                         return (errorCorrectionLevel.ordinal() << 3) | (int) dataMask;\r
 132                 }\r
 133                 \r
 134                 public  override bool Equals(System.Object o)\r
 135                 {\r
 136                         if (!(o is FormatInformation))\r
 137                         {\r
 138                                 return false;\r
 139                         }\r
 140                         FormatInformation other = (FormatInformation) o;\r
 141                         return this.errorCorrectionLevel == other.errorCorrectionLevel && this.dataMask == other.dataMask;\r
 142                 }\r
 143         }\r
 144 }